Microtunneling
A trenchless construction method for installing pipelines with the following attributes – remote control, guidance, pipe jacking, and continuous support.
Midi-Rig
Steerable surface-launched equipment for the installation of pipes, conduits and cables. Applied to intermediate sized drilling rigs used as either a small directional drilling machine or a large guided boring machine. Tracking of the drill string may be achieved be either a downhole survey tool or a locator.
Million Gallons per Day (MGD)
US customary unit for flow measurement. One MGD equals 43.81 liters per second.
Mini-Horizontal Directional Drilling (Mini-HDD)
A term sometimes applied to Guided BoringMethod for the installation of pipes, conduits and cables using a surface-launched drilling rig. A pilot bore is drilled using a rotating drill string and is then enlarged by a back reamer to the size required for the product pipe. The necessary deviation during the pilot boring is provided by a slanted face to the drill head, an asymmetric drill....
Mixed Face
An interface within the excavated tunnel zone between two geological units that have a significant contrast in engineering properties (e.g., rock overlain by soft ground, or very soft, low-strength soil overlain or underlain by a very stiff, high-strength soil).